Sophisticated weapons are not the only technological firsts of the Persian Gulf War. Here at home, people are using personal computers equipped with modems to communicate with GIs serving in the gulf, get the latest news, share opinions and help mobilize support for and against the war.

For the first time in history, combat troops are receiving electronic letters from home. CompuServe, GEnie and Prodigy are offering one-way electronic mail service so that people in the United States can send messages to troops serving in the gulf.

GEnie and Prodigy transmit the messages directly to Saudi Arabia where they are laser printed, stuffed into envelopes and taken to military post offices for delivery. CompuServe prints the letters in the United States and delivers them to the Army post office in New York, which airlifts the mail to the gulf.

The actual delivery time depends on the military, but the letter reaches Saudi Arabia within hours. A Prodigy subscriber reported that one of her messages was delivered to a serviceman the same day -- most of the others were within two days.

GEnie, a service of General Electric, is offering the service at no cost to anyone with a PC and a modem, regardless of whether he or she is a subscriber. CompuServe and Prodigy make it available to members at no additional surcharge.

Messages must be addressed to a specific recipient and must include the person's name, rank, unit or ship and (optional with Prodigy) Social Security number. Anyone interested in taking advantage of GEnie's free "Letters from Home" offer should call 1-800-638-9636 for recorded instructions. For information about Prodigy, call 1-800-776-3449. CompuServe can be reached at 1-800-848-8199.

The on-line services also provide up-to-the-minute war news. On-line access to late news may not seem so important in this era of 24-hour TV and radio news, but the level of detail and the ability to choose the stories you wish to read can provide you information that's just not available on TV. All the services also allow you to print the stories and, with the exception of Prodigy, allow you to save the information on your hard disk.

CompuServe posts reports from United Press International and Associated Press. GEnie compiles and edits stories from UPI, Reuters and various foreign news agencies. Prodigy, which also displays area maps and other graphics, has its own newsroom where editors compile information from news wires and other sources.

CompuServe has added a "Gulf Crisis Menu" that serves as a gateway to war-related news and features. Prodigy features war-related headlines on its sign-on screen with in-depth features available from a special topics menu. GEnie members can go to the NewsGrid section for late war information.

The services also offers forums, or bulletin boards, where users can exchange information and opinions about current events. Participating in such a forum is like attending a national town meeting. More than 1,000 messages were posted on Prodigy's Closeup bulletin board the first night of the U.S. attack on Iraq.

Other firms also are offering war-related computer-communications services.

The Well is a Sausalito, Calif.-based on-line service that appeals to computer professionals and others with an interest in communications. The service now has a Middle East forum that is being used to debate policy issues, inform users about events and provide information about what people are doing to promote or protest the war. For information about The Well, call 415-332-4335.

The anti-war movement is also using computer communications technology. PeaceNet, a San Francisco-based service which can usually be accessed via a local phone call, links peace activists throughout the world. PeaceNet provides details on recent and upcoming demonstrations along with information about anti-war activities taking place in the United States and abroad.

Subscribers can use the service to send electronic mail to other activists in the United States, Israel, the Soviet Union and other countries. The service is being used by professional organizers, church groups and members of peace groups. For information, call 415-923-0900.

Readers' comments are welcomed, but the author cannot respond individually to letters. Write to Lawrence J. Magid, P.O. Box 620477, Woodside, Calif. 94062, or contact the L. Magid account on the MCI electronic mail system.